Easiest way (but not the prettiest) is to just choose the dodge/burn tool.. Set it to dodge at about 50% opacity/fuzzy feathered brush, and paint over the area you want to brighten.

Another nice way to do it, is to make a couple different layers. Give one a screen, add layer mask- paint back in the eyes. Then do a multiply layer with about 40% opacity, and paint back in the iris of the eyes.

It's ok! I'm still learning all of this, there is SO much you can do with editing. =)

If you go to "layers" click duplicate layer twice.

There are different layer modes, all set as drop down boxes in your layers pallette.

Play around with it..and get a feel for what the different modes do.

Screen-is great for brightening people and other subjects. But do set the opacity bar (just under the mode drop down menu in the layers pallete) to something that doesnt' look otherworldly.

Multiply- essentially adds contrast and darkens things a bit..but also has a nice saturating effect on colors.

If you add a layer mask (I always choose black) by right clicking the top layer then the "add layer mask" it will "hide" the layer. In order to "see" the layer you multiplied/screened/ or otherwise altered in some way...you have to "paint" with a white brush (the mask is black) to reveal what is under the mask. Then, only the areas you choose will be revealed.

Does that help a bit? There are lots of great tutorials on the web, too.

Gimp scares me! As soon as I finished downloading it & opened it up I immediately had to close it because it overwhelmed me, lol. I need to get up the courage to open it back up again & start learning/looking at the tutorials.